You may want to report that, if you haven't already. But yeah, that's pretty annoying.
I end up reporting issues like this around twice a lesson, which gets tiring. It's especially bad in the later sections of the tree, I stopped reviewing old lessons because it's so picky (like, in one instance they wanted you to translate 往左走 as "turn left", and didn't accept "go left", then in another instance they wanted "go left" and didn't accept "turn left"). I reported this but the comments are littered with complains from 2 months ago too.